1. Field of the Invention
The invention relates to a new process for the production of 2-aryl-2H-1,2,3-triazoles.
2. Background Art
2-Aryl-2H-1,2,3-triazoles, especially those in which the triazole ring has a substituent in the 4 position, have insecticidal and acaricidal effects [European Published Patent Application No. 350237].
A known process for their production starts from arylhydrazones of .alpha.-hydroxyiminoaldehydes or -ketones, which are cyclized with oxidizing agents, such as, copper sulfate. The thus-obtained N-oxide can be reduced in a known way. The necessary hydroxyimino-arylhydrazones can be produced by reaction of the corresponding arylhydrazine with the corresponding .alpha.-dicarbonyl compound and oximation of the thus-obtained .alpha.-carbonyl-arylhydrazone. The process is laborious and, because of the oxidation and reduction steps in the course of the synthesis and in the production of the arylhydrazine necessary as an initial material, exhibits other drawbacks, especially the one that the process results in a great amount of waste.
If the hydroxyimino-arylhydrazone is first acylated the thus-obtained acyloxyimino-arylhydrazone can also be converted directly into the desired triazole by adding a base so that the formation of the N-oxide and its reduction are avoided. However, instead as when the base is used for cyclization, a salt of the carboxylic acid corresponding to the acyl group accumulates as waste.